Age-related hearing loss or presbycusis poses enormous humanitarian and economic challenges to society. In the US, it is estimated that 23 percent of people aged between 65 and 75 years of age, and 40 percent of people over 75 years of age have presbycusis, and the number of people suffering from this disorder is expected to grow dramatically as the population of older people increases (Someya et al., Neurobiol. Aging 20:1613 [2007]).
Presbycusis is the loss of hearing that gradually occurs in most individuals as they grow older. Hearing loss is a common disorder associated with aging. The loss associated with presbycusis is usually greater for high-pitched sounds or high frequency sounds.
There are many causes of presbycusis. Most commonly it arises from pathological changes in the inner ear of a person as he or she ages, but presbycusis can also result from pathological changes in the middle ear or from complex pathological changes along the nerve pathways leading to the brain. Presbycusis most often occurs in both ears, affecting them equally. Because the process of loss is gradual, people who have presbycusis may not realize that their hearing is diminishing. With presbycusis, sounds often seem less clear and lower in volume. This contributes to difficulty hearing and understanding speech.
Sensorineural hearing loss is caused by disorders of the inner ear or auditory nerve. Presbycusis is usually a sensorineural hearing disorder. It is most commonly caused by gradual changes in the inner ear. The cumulative effects of repeated exposure to daily traffic sounds or construction work, noisy offices, equipment that produces noise, and loud music can cause sensorineural hearing loss. Sensorineural hearing loss is most often due to a loss of hair cells (sensory receptors in the inner ear). This can occur as a result of hereditary factors as well as aging, various health conditions, and side effects of some medicines (aspirin and certain antibiotics).
Presbycusis may be caused by changes in the blood supply to the ear because of heart disease, high blood pressure, vascular (pertaining to blood vessels) conditions caused by diabetes, or other circulatory problems. The loss may be mild, moderate, or severe.
Sometimes presbycusis is a conductive hearing disorder, meaning the loss of sound sensitivity is caused by abnormalities of the outer ear and/or middle ear. Such abnormalities may include reduced function of the tympanic membrane (the eardrum) or reduced function of the three tiny bones in the middle ear that carry sound waves from the tympanic membrane to the inner ear.
There are many strategies to help people with presbycusis. Hearing aids may be recommended for some individuals. Assistive listening devices can provide further improvement in hearing ability in certain situations. One example of such a device is the built-in telephone amplifier. Another example is FM systems that make sounds clearer, with or without a hearing aid, by delivering sound waves like a radio. Training in speechreading (using visual cues to determine what is being spoken) can help those with presbycusis to understand better what is being said in conversations or presentations.
Nonetheless, no preventative or therapeutic interventions have been developed for presbycusis.